Electrical conductor



.Fan. 12, 1932. I c, w, ABBOTT 1,841,348

ELECTRICAL CONDUCTOR Filed Oct. 9, 1922 I N VEN TOR. M w

A ORNEYJ Patented Jan. 12, 1932 UNITED STATES PATENT OFFICE CHARLES WILLS ABBOTT, OF HARTFORD, CONNECTICUT, ASSIGNOR, BY MESNE ASSIGN- MENTS, 1'0 GENERAL CABLE CORPORATION, OF NEW YORK, N. Y., A. CORPORATION OF NEW JERSEY ELECTRICAL CONDUCTOR Applicationfiled October 9, 1922. Serial No. 593,263.

This invention relates to insulated and protected electrical conductors which are particularly adapted for use in house wiring although not at all confined to such use.

For a great many years it has been found necessary and desirable in certain wiring of this general class to protect the ordinary rubber and braid insulated wires from moisture and abrasion and to confine any fire which may occur because of over loading of the circuits or otherwise, and also to protect the ordinary rubber and braid, which is relatively inflammable, from fire occurring in proximity to the wiring. 7

One of the early structures designed for this purpose consisted of a tube which was built up by wrapping a tough rag fibre around a steel mandrel which tube was covered with a Woven outer jacketof cotton yarn, the jacket being impregnated with relatively fire and moisture proof compounds of an asphaltum base, and dusted with finely ground mica which was supposed, not only to improve the appearance of the tube, but also increase its fire-resisting properties. This tube Wasin- 'variably ofvcircular cross section and was designed, to have a conductor drawn through.

Since this original form was placed on the commercial market many developments which, however, embodied the same broad principles, have appeared. The main differences between these later modifications and the original form of tube lie in the use of various materials to cheapen the production, in the interweaving of thehelically wound strip vwith cotton yarn in an attempt to form a more substantial inner tube, in the substitution of a cotton braid for the original woven outer jacket and in the use of various 'impregnating compounds of'an asphaltum or' pitch base.

- There have been considerable disadvantages attending each of the constructions on the commercial market. For instance, while the tubes have been intended to be flexible so that they may be drawn into the necessary configurations, they'have been found, actually, to be soafl'ected by the warm weather that when they fulfill the necessary conditions of flexibility the fire and moisture resisting impregnating compounds often become so soft that it is diflicult, if not impossible, to advantageously use the tubes. This is partly due to the fact that they are so easily deformed or abraded at this time that they may not be drawn into the necessary configurations without destroying or seriously affecting their protective properties. On the other hand in cold weather the tubes often become so brittle that whenit is attempted to bend them into the necessary forms for the reception of the conductors they are broken or the impregnating compounds are chipped off, so that at these points at least they no longer possess the protective qualities necessary.

In commercial practice these tubes have been made with an inside diameter greater than that of the outside diameter of the conductors which they house; this to permit the conductors to be drawn through them. This results in a considerable disadvantage in that the conductors are surrounded when so encased, by a continuous air space which may form a flue for any fire which may originate by an overloading of the circuits and a consequent ignition of the relatively inflammable rubber insulating compound required in proximity to the wire. Furthermore, the

presence of the cotton yarn which is interwoven with the helical strip in the later developed forms of this tube enhances the possibility of the fire obtaining considerable headway, as it has been found impossible to successfully impregnate that portion of the cotton yarn exposed upon the inside of the tube, with moisture and fire resisting compounds without interfering with the ease with which the conductors may be drawn thnough the tubes. Moreover, the interiorly exposed. and unimpregnated portion of the cotton yarn is free to and does absorb moisture to the detriment of the circuits.

Furthermore, where electrical circuits must be established in restricted spaces it is practically impossible to draw the various qualities. I p

My invention not only overcomes many of the disadvantages which have been present in the commercially used forms of protecting tubes but presents many advantages in installation, protection and method of manufacture.

the purpose of this description l have illu rated in the accompanying drawings, a preferred illustrative form of my invention, and therein,

l is perspective view of a short section of assembled conductors showing a preferred embodiment of the invention and having the several sheaths of material progressively removed to show the interior construc ion;

lF nre 2 is a section on the line of big e 1..

Referring to the embodiment illustrated, ordinary code electrical conductors 1, having rubber insulation 2 and braid or other suit able coverings 3, are used. Each of these insulated and covered conductors 1 is rovided with an armor 4, consisting prefera ly of a helically wound strip of relatively flexible material such as paper which closely embraces said conductors and which provides mechanical as well as electrical protection for the conductors. If a helically wound covering is used, it is preferably so applied that the edges of adjacent convolutions abut each other. The wires thus wound are covered with a second protective covering 5 which, in the illustrated embodiment, takes the form of a braided, woven or knitted fabric jacket.

The helically wound armor 4 and the jacket 5 are treated with a moisture and fire resisting compound.

The preferable compound for this purpose contains the necessary ingredients in a finely divided condition and is distinguishable by its relatively low-adhesive properties, the object being to treat, in effect, the strands of the jacket 5 individually without binding them together. Such a compound will, to a degree, pass through the jacket 5 and be absorbed to some extent by the armor 4 but, due to the absence of adhesive properties will permit the armor and jacket to move relatively when the assembled product is flexed.

Two or more of the conductors thus armored, jacketed and treated are preferably assembled either by placing them side by side in the manner shown in the drawings or by twisting them together and, assembled in either manner, are bound together by additional protective means which in the illustrated embodiment takes the form of a braided, woven or knitted sheath. This fabric sheath 6 is impregnated with a moisture and fire resisting compound which also acts as a finishing compound. This compound is of such a nature that, if desired,'it may contain any distinctive color and willimpart the same to the finished product. Furthermore, this race-s een compound will not discolor or otherwise feet paints which may be applied to ii seinbled product when installed, as guished from the mica-dusted tube does not afford a good paintina su consequently will not admit of a proper 1, ish when used in exposed places.

In building up the illustrated form of invention hereinbefore described, the i lated and covered conductors are ill with armor 4:. Care is QXCIClb selection of the material used in since it must satisfy many cond'tior must not be so soft or porous that it provide dependable mechanical and protection or that it will break wh jccted to the necessary tension in the operation, or that it will separate "1 its volutions while being applied or that 1 absorb greater quantities of the fire d ture resisting compounds than is inten and desirable. And yet, on the other hanc, it must not be so inflexible that it will break down or fracture when being wound on the conductors or that it will fail to absorb the necessary quantity of the fire and moisture resisting compound. l have found a tough fibrous paper of approximately .0530 of an inch in thickness and approximately of an inch in width to be admirably adapted for this purpose.

After the material 4 has been wound upon each of the conductors to form the armor, the jacket 5 of the illustrated embodiment is either braided, woven or knitted thereon. The thus armored and jacketed wires may now be passed through a relatively cold fire and moisture resisting com ound, some of which is absorbed by the jac (ets 5. A sufiicient quantity of the compound to properly treat the armor 4 is transmitted through the acket 5.

In the former types which have liereinbefore been described it was necessary to apply the moisture and fire resisting material in a heated condition to insure penetration and furthermore, to apply it in such quantities that it would assist in maintaining the structural rigidity. It was partly because of this fact that the tubes became brittle in cool weather and soft in warm weather. In the case of the present invention the ultimate structure does not depend for its rigidity upon the fire and moisture resisting material but upon the structure alone.

The thus armored, jacketed and moisture and fire resistant conductors are then assembled in groups of two or more and either arranged side by side or twisted together. Thus arranged the outer sheath is applied. This outer sheath closely binds the conductors together, adding materially to the rigid ity imparted by the armor and jacket, and assisting these elements also in preventing abrasion of the wires.

The sheath having been applied, the entire also structure is passed through a second compound which renders it not onlyhighly fire and moisture resistant but also imparts any desired color to the sheath. This compound is of such a nature and is so applied that it preferably does not cause the outer sheath to adhere to the jacket 5. The compounds used are such that they rapidly dry so that the product may be bundled in desired lengths as it passes from the sheath-applying machine. I

I have foundthat a fire and moisture resistant compound consisting of barium sulphate and china wood oil thinned with coal tar naphtha is admirably adapted for the treatment of the armor 4 and jacket 5 and that a compound containing zinc oxide and water glass as its principal ingredients to which coloring matter is added, is admirably adapted for the impregnation of the outer sheath.

The invention is not to be limited in this phase to the use of these'particular compounds for although as before said they are adapted for such use, they are not by any means the only fire and moisture resistant compounds which can be used.

From the foregoing description it will be seen that the building up of an armor which closely embraces the electrical conductors protects the conductors against abrasion and eliminates the objectionable fire flues'which were present in the tubes heretofore used.

Furthermore, the structure impregnated as described forms an effective fire resistance which will not be abraded and broken down by the blows which are encountered in installation and use and which is relatively unaffected by changes in temperature. All of the exposed parts of the structure being moisture proofed, there will be no absorption of moisture to the detriment of the circuits. This is a distinct advantage over the old type tubes which contain untreated cotton fibres.

The various components of the structure being treated with only sufficient compound to render them moisture and fire resistant, the structure possesses the requisite flexibility without detriment to the moisture and fire resistant features which is a distinct advanstage over the old type tubes where the moisture and fire resistant compounds were applied not only in sufiicient quantities to provide protective qualities but also a give body to the tubes. The loading of'the tubes with sufiicient com ound of the character necessarily used to give the required body operated to destroy the flexibility, rendering them soft in warm weather and brittle in-cold weather.

, Moreover, the conductors protected in the manner of my, invention may be installed to advantage with minimum labor and expense since it only. requires a single length to complete the circuit,whereas in the old type of tubes each of the tubes accommodated only one conductor and to complete a circuit it was necessary to install at least two tubes.

The inclusion of the two conductors in the one structure in the flat form is distinctly advantageous when conductors are drawn into restricted spaces and also when applied to exposed surfaces such as ceilings, walls, etc. inasmuch as the application directly to the exposed places presents a structure which will readily adapt itself to the trim and may be colored in harmony with the adjacent surface. Furthermore, the flexibility of the structure makes it possible to follow the bends of the trim of a room without destroying the protective features of the structure.

While I have described a particular embodiment of my invention, it has merely been for the sake of illustration and I do not wish to be limited to that particular embodiment as it is obvious that many changes in details of the claims.

I claim:

1. The method of forming ductors which consists in treating each of two wires with rubber of a quality to be relaofconst'ruction may be made within the scope electrical coritively flexible but not fire proof,oovering each of said wires so treated with liquid absorbent braided material to form a closely fitted 'acket, covering the same with armour of paper.

enclosing the separate wires so wrapped in jackets of braided material, saturating each conductor thus formed with a substantially non-adhesiv-e fire and moisture proofingcompound binding the separate wires together with an enclosing" sheath and treating the whole structure with, fire and moisture proofing compound containing zinc oxide and watersglass. I I

2. An electrical conductorcomprising two code wires having rubber and braid'insula tion, an armour enclpsing each code wire consisting of spirally wound paper treatedvwith' barium sulphate and china wood oil thinned with coal tar naphtha, a braided casin efi-f closing each armoured code wire, said raid being treated with a compound similar to that used in connection with said armour to render the same fire and moisture proof, and a braided sheath enclosing and binding together the whole, said sheath being treated with zinc oxide and water lass, said armour and braided casing being re'efto more relatively to prevent breaking thereof when said conductors are flexed.

3. An article of manufacture comprising, in'combination, a plurality of electrical conductors, a sheath. of plastic compound immediately surrounding each, conductor, a braided jacket surrounding each of said insulating sheaths, a protective armor wrapping' comprising a strip of paper of substan tial thickness closely wound about each of said jacketsya second braided jacket imn'iediately surrounding each armored cone ctor, and an outer braided fabric jacket surrounding said conductors and binding them together.

4-. The method of forming electrical conductors Which comprises enclosing each of two metallic conductors in a rubber sheath, forming a fabric braid over the rubber sheath, tightly serving a tough armor of fibrous material over said braid, enclosing the Whole in a fabric braid, saturating each conductor thus formed with a fire and moisture proofing compound of substantiall nonadhesive qualities which Will be transmitted 315 to and be absorbed by the fibrous armor but Without binding the outer fabric braid thereto, binding the separate Wires together with an enclosing sheath and treating the Whole with a substantially non-adhesive tire and 2G moisture proofing compound.

5, An electrical conductor comprising a Wire having rubber and braid insulation, an armor enclosing the insulated Wire, said armor comprising spirally Wound paper treated with barium sulphate and china Wood oil thinned With coal tar naphtha, a braided casing enclosing the armored Wire, said braid being treated With a compound similar to that -used in connection With said armor to to render the same fire and moisture-proof, and

a fabric sheath enclosing said armored conductor, said fabric sheath being treated With a fire and moisture-resistant compound.

In testimony whereof, l[ have signed my at name to this specification this 7th day of October, 1922.

CHARLES WILLS ABBOTT. 

